Quantum mechanics-based structural analysis of phenolic glycosides from Cuscuta japonica seeds with protective effects against H2O2-induced oxidative stress in SH-SY5Y cells

Japanese dodder (Cuscuta japonica Choisy) is a parasitic plant with diverse pharmaceutical properties that has demonstrated great promise for the development of dietary supplements and herbal medicines. A systematic phytochemical investigation of dodder seeds yielded 12 previously undescribed aromatic glycosides (1−12) and eight known constituents (13−20) from various groups, including phenolics, flavonoids, and lignan glycosides. Compound structures were determined using a combination of high-resolution electrospray ionization mass spectrometry and nuclear magnetic resonance (NMR) spectroscopy. Moreover, quantum mechanics-driven ¹H iterative full spin analysis revealed intricate NMR spectral details for the isolated glycosides, including multiplicities and coupling constants that were previously ambiguous, providing crucial insight into the presence of higher-order resonance effects in the sugar units as well as long-range couplings in unsaturated molecules. Furthermore, the abilities of the plant extract as well as compounds 1, 2, 4–7, 10, 11, and 14–20 to restore cell viability and reduce reactive oxygen species production in SH-SY5Y cells suggest that C. japonica and its isolates are potential antioxidant neuroprotective therapeutic candidates.